Method of preparing transfer sheets



April 24, 1962 METHOD OF PREPARING TRANSFER SHEETS Filed Nov. 20, 1959INVENTOR. J a/y/d; A. fi an mafi D. A- NEWMAN "3,031,327

United States Patent 3,031,327 METHOD OF PREPARING TRANSFER SHEETSDouglas A. Newman, Glen Cove, N.Y., assignor to Columbia Ribbon andCarbon Manufacturing Co., Inc, Glen Cove, N.'Y., a corporation of NewYork Filed Nov. 20, 1959, Ser. No. 854,342 11 Claims. (Cl. 117-364) Thisinvention relates to a new method of preparing novel transfer sheets andribbons.

Conventional carbon papers have been known for many years and are themost common transfer sheets in use today. These sheets are prepared bycoating paper with a layer of melted wax-carrying pigment. Upon cooling,there results a transfer sheet carrying a layer of pressure-transferablewax having homogeneously dispersed therein the pigment, such as carbonblack or graphite.

It is recognized that these known carbon papers have many'seriousdisadvantages. Because of the homogeneous distribution of the pigmentthroughout the wax layer, the transfer sheet is dirty-to-the touch andthus must be handled by the user with extreme care. It is also a problemin that the transferred image such as typing or writing is likewisedirty-to-the-touch and becomes smudged upon ordinary handling.

Still another important disadvantage of these known carbon sheets is thelarge amount of pigment which must be used, most of which is wasted.

It is an object of the present invention to prepare transfer sheets andribbons of the carbon paper type which have a light colored appearanceand which are clean-tothe-touch The foundation may be paper or anyplastic film such as cellulose acetate, cellophane, polyethyleneterephthalate (Mylar), vinyl polymers, etc.

It is another object of the present invention to prepare carbon papersand ribbons which transfer smudgeproof images of colored or magneticpigments.

It is a further object of the present invention to prepare carbon papersand ribbons using less pigment than heretofore possible.

These and other objects are accomplished according to the presentinvention.

In the drawing:

FIGURE 1 is a diagrammatic cross-section view, to an enlarged scale, ofthe transfer sheets of the present invention.

FIG. 2 is a, diagrammatic cross-section view, to an enlarged scale, of acopy sheet carrying an image transferred from the present transfersheets.

I have found that the many difficulties existing through the use ofconventional carbon paper may be avoided and that cleaner andbetter-appearing transfer sheets and ribbons. may be prepared accordingto the present discovery.

This invention is. accomplished by applying a pigment solution ordispersion, to the surface of any conventional frangible waxlayercarried upon a foundation sheet and heating the; mass, tov the softeningor fusion temperature of the wax whereby the liquid carrier for thepigment is evaporated. oil and the. pigment is allowed to seep into the.wax layer 11 and. be absorbed thereby. Thus, upon cooling, the wax onthe transfer medium again solidifies over the. pigment layer 12 which isheld just below the wax surface. Thus. the pigment layer is insulated.against contact during handling in that it is o ercoated by thesolidified wax- Likewise it is insulated against contact with the;foundation sheet in that it has not penetrated completely through thewax layer to the foundation sheet. as shown by FIG. 1 of the drawing.

Upon the. application of pressure against the back of the. transfermedium as by a pen, pencil,ftype.bar or styheated or fused in thedescribed manner.

2 lus, an image transfers to a copy sheet 20 and is smudgeproof in thatit has no pigment at its surface, the surface of the image being theportion of the transfer layer which was adjacent the foundation on thetransfer sheet. The surface of the image is thus of clear wax and thepigment layer 12 is held beneath this surface, as shown by FIG. 2 of thedrawing. The use of temperatures in the range of l50-250 F. is necessaryto insure that the wax softens or melts to just the right degree toallow the pigment to be absorbed and covered thereby. The duration ofthe heating depends upon the melting point of the wax layer employed andthe temperatures used, but in general, heating continues for only thatperiod of time required for the sheet to pass the heating element at thenormal speed of a coating machine.

In another form of the invention, a non-volatile plasticizing agent isadded to the pigment dispersion. After application of the pigmentdispersion to the wax layer and heating to fusion, the plasticizingagent causes the pig ment to wet down and blend or commingle at theinterface with the wax layer. Sheets and ribbons prepared in this mannerhave increased properties of dry rub and the transferred images haveincreased resistance to smudging. Plasticizing agents comprising oilssuch as vegetable oils; polyalkylene glycols such as water-insolublepolybutylene glycol; and esters such as butyl stearate and tricresylphosphate provided excellent results.

In still another form of the present invention, a bonding agent is addedto the pigment dispersion with or without the plasticizing agent and itaids in the formation of a better dispersion, mixed for instance in aWaring Blendor. The dispersion is coated on the wax layer and Thisheating brings about commingling at the interface thereby providing arelatively hard surface having the pigment well sealed, both by thebonding agent and by the wax underlayer. Apparently the underlayeradmixes with the bonding agent so that an exceptionally clean sheetresults. As the bonding agent, any material may be used which is atleast partially miscible with the wax layer of the foundation. Resinousmaterials such as ethyl cellulose, methyl cellulose and hydroxyethylcellulose may be used. Also, any frangible wax, such as those employedin the wax layer of the fundation, as well as spermaceti or cetylalcohol, may be used successfully. It is preferred that the bondingagent be not only miscible with the wax underlayer but also at leastpartly soluble in the vehicle for the pigment, such as alcohol, water,petroleum naphtha or ethyl acetate, for instance. In this respect, ethylcellulose is preferred as the bonding agent with ethanol as the solvent.It should be noted that when a water-soluble binder is used with wateras the solvent, conventional wetting agents such as Aerosol AY should beadded.

In still a further embodiment of the present invention, the wax layer onthe foundation sheet may be pigmented in the conventional manner priorto its application to the paper. It has been found for instance that ifthe wax layer is pigmented with a blue or other light colored pigmentsuch as titanium dioxide or other white pigment, and then fusion coatedwith a black or other dark colored pigment, the transfer medium has anappearance much lighter than if the blue or white and black were mixedas one, but the image transferred under pressurev has a color darkerthan would have been expected from the light appearance of the transfersheet. This appears to be due to a blending or coalescing of thepigments under pressure. Quite unexpectedly, in the case where whitepigment is employed in the wax layer, it has been found that the formedtransfer sheet is capable of duplicating on black or white copy sheets.When duplicating for instance onto a white copy sheet the formed imageappears black, apparently due to a blending of the white pigment of theimage with the white background. When duplicating with the same transfersheet onto a black copy sheet, the formed image appears white,apparently due to a blending of the black pigment of the image with theblack background. This feature is quite important, for instance, in thepreparation of debit-credit sheets wherein either the debit or creditcolumn is given a black background. Thus, while using only a singletransfer sheet, the credit items appear on the receipt or copy sheet inblack while the balance or debit items appear in white, or vice versa.Likewise it has been found that titanium dioxide or other white pigmentmay be incorporated in the wax layer on the foundation sheet andmagnetic iron oxide or other magnetic pigment may be applied by thefusion method. Upon transference, the white pigment covers the magneticiron oxide so that the image itself is hidden or appears quite light butremains magnetically sensible in very way.

The following examples are set forth by way of illustration and shouldnot be considered as limitative.

Example I This example shows the basic step of applying an unmodifiedpigment dispersion to a wax coated sheet. The steps are as follows.

(1) Ordinary kraft paper is coated with a conventional thickness of alayer of a wax composition having the following recipe:

(2) This wax coated paper is then coated on its wax surface with apigment dispersion such as graphite dispersed in alcohol.- The amount ofgraphite used depends upon the tone-strength desired in the transfersheet and adjustments are well within the purview of one skilled in theart.

(3) Some of the product of step 2 is then heated to a temperature of 100F. to drive off the alcohol solvent. Upon cooling, this transfer sheetis useless in that the graphite merely lies on the wax surface and rubsofi when the sheet is handled.

(4) The remainder of the product of step 2 is now steam heated to atemperature of 2l2230 F. for a short period of time to allow the wax tofuse and absorb the graphite. Heating is stopped and the sheet allowedto cool. The transfer sheet is clean to the touch and yieldssmudge-proof images under pressure.

Example 11 This example illustrates the use of a binder-containingpigment dispersion, a plastic foundation material and magnetic pigment.

(1) A thin sheet of polyethylene terephthalate (Mylar) film having athickness of 0.5 mil is overcoated with a layer of pressure-transferablewax of the following formulation:-

(2) The wax coated Mylar is then coated with a pigment dispersion ofmagnetic iron oxide and alcohol containing ethyl cellulose binder inabout the following proportions:

Percent Magnetic iron oxide 39.3 Alcohol (ethanol) 58.7 Ethyl cell 2.0

(3) The product of step 2 above is steam heated to a temperature of 22020 F. for a few minutes to allow the wax to melt and absorb the wettedpigment. After cooling, the transfer sheet has excellent qualities ofcleanliness and the formed image is smudge-free and completely sensibleto magnetic sensing means.

Example III tive formulations.

Formulation 1: Percent Carbon black 1 Alcohol (ethanol) 98 Ethyl cell 1Formulation 2:

Graphite or carbon black 1 Alcohol (ethanol) Dow Polyol B-500(water-insoluble polybutylene glycol) (3) The individual sheets eachcoated with these different pigment dispersions are then heated to atemperature between 220-230 F. for a short period of time to allow thewax layer on the foundation sheet to melt and absorb thebinder-containing pigment dispersion. Upon cooling, these transfersheets are completely clean to the touch, light in appearance and upontransfer the formed image is dark colored and sumdge-free.

The materials and proportions set forth in these examples are merelyillustrative and variations may be made according to the knowledge ofthe art. For instance, any of the conventional waxes of the animal,vegetable, mineral or synthetic variety may be substituted for those ofthe examples and the proportions may be varied according to hardness ortackiness desired in the final product.

As the pigment dispersion, it has been found convenient to usecommercially available dispersions of carbon black or graphite inwater-insoluble polyalkylene glycols such as DAG-197 which is a 10%dispersion of graphite in water-insoluble polybutylene glycolmanufactured by the Acheson Colloids Company. Likewise a 20% dispersionof graphite in isopropanol, available from Acheson Colloids Companyunder the name DAG-154, may be used. Alternatively the pigmentdispersion may be compounded by mixing the desired pigment in thedesired amount with Dow Polyol B 500 which is a water-insolublepolyalkylene glycol.

Also, in place of the pigments named, hectograph dyes such as crystalviolet or planographic pigments such as nigrosine black and Bismarckbrown may be employed.

Variations and modifications may be made within the scope of the claimsand portions of the improvements may be used without others.

I claim:

1. The method of preparing transfer sheets which are clean to the touchwhich comprises the steps of coating a foundation sheet with a layer ofpressure-transferable wax, applying to the wax surface a dispersion of apigment, a non-volatile plasticizing agent for said wax and asure-transferable wax, prior to application of the pigment dispersion,contains a pigment different from that of said pigment dispersion.

3. The method of claim 1 in which the pigment comprises magneticpigment.

4. The method of claim 1 in which the plasticizing 7 agent comprises awater-insoluble polyalkylene glycol.

5. The method of claim 1 in which the temperature of heating ranges from150 F. to 250 F.

6. The method of preparing transfer sheets which are clean to the touchwhich comprises the steps of coating a foundation sheet with a layer ofpressure-transferable wax, applying to the wax surface a dispersion of apigment, a volatile carrier and a binding agent which is soluble in saidcarrier, heating to a temperature sutficiently high to soften the waxlayer, allow the pigment to be absorbed thereby and evaporate thevolatile carrier, and

ment is held just below the wax surface and is overcoated by the cooled,solidified wax and said binding agent.

7. The method of claim 6 in which a non-volatile plasticizing agent ispresent in the pigment dispersion.

s. The method of claim 6 in which the binding agentcomprises ethylcellulose.

9. The method of claim 6 in which the pigment'comprises magneticpigment.

10. The method of claim 6 in which the foundation sheet is a plasticfilm.

11. The method of claim 6 in which the temperature of heating rangesfrom F. to 250 F.

References Cited in the file of this patent UNITED STATES PATENTS1,189,939 Goldsmith July 4, 1916 1,864,097 Sherman June 21, 19321,925,235 Dixon Sept. 5, 1933 2,063,226 Braunstein Dec. 8, 19362,744,031 Mumma May 1, 1956 2,912,344 Newman et al Nov. 10, 1959 FOREIGNPATENTS 393,904 Great Britain June 15, 1933

1. THE METHOD OF PREPARING TRANSFER SHEETS WHICH ARE CLEAN TO THE TOUCHWHICH COMPRISES THE STEPS OF COATING A FOUNDATION SHEET WITH A LAYER OFPRESSURE-TRANSFERABLE WAX, APPLYING TO THE WAX SURFACE A DISPERSION OF APIGMENT, A NON-VOLATILE PLASTICIZING AGENT FOR SAID WAX AND A VOLATILECARRIER, HEATING TO A TEMPERATURE SUFFICIENTLY HIGH TO CAUSE THE WAX TOSOFTEN, ALLOW THE PIGMENT TO BE ABSORBED THEREBY AND EVAPORATE THEVOLATILE CARRIER, AND THEN COOLING TO FORM THE TRANSFER SHEET IN WHICHTHE PIGMENT IS HELD JUST BELOW THE WAX SURFACE AND IS OVERCOATED BY THECOOLED, SOLIDIFIED WAX.